PROJECT SUMMARY Craniofacial reconstruction is required after trauma, tumors, and for craniofacial disorders. Bone grafts and synthetic scaffolds have resulted in limited success. Bone morphogenetic proteins (BMPs) stimulate the production of bone and cartilage, and are necessary for tooth development, palate closure and normal craniofacial development. BMPs are also required for bone repair and can stimulate stem cells to take on cartilage and bone fate. We recently discovered that ion channels control the secretion of BMP in the fruit fly. Our hypothesis is that ion channel activity regulates BMP secretion in mammals in a conserved mechanism. In support of this hypothesis, mice with disrupted potassium channel function have decreased activation of BMP signaling and similar phenotypes to BMP mutants. If our hypothesis proves correct, electrical stimuli or small molecules that affect ion channel activity may provide the ability to control release of BMP for proper bone and tooth development and regeneration. Our long-term goal is to use a novel approach of manipulating cells to secrete endogenous BMP to encourage craniofacial bone development. The first step towards this goal is to determine the mechanism by which an ion channel contributes to BMP signaling in mammals. In this proposal, we use the Kir2.1 potassium (K+) channel to determine the molecular connection between ion conductivity and BMP signaling in mammals. Humans and mice with mutations in Kir2.1 have congenital craniofacial defects including cleft palate, dental defects, and micrognathia showing that this channel plays an essential role in craniofacial development. Aim 1 determines where Kir2.1 acts in the BMP pathway in mammals using epistasis and rescue experiments. Aim 2 tests the hypothesis that ion channels regulate BMP secretion in mammals as they do in flies. In other cell types, ion channels influence intracellular calcium to regulate secretion. In Aim 3, we determine how intracellular calcium influences BMP release. The proposed experiments will lay a foundation for future studies to harness the potential of ion channels to stimulate tissue growth and regeneration.